“The protection of myocardium” is a hot subject in the research of the cardiology and cardiac surgery. The latest information indicates that the myocardium cell would take place change in the condition of ischemia and hypoxia, such as intra-cellular over-loading of the calcium, generation of free group, damage of the cell membrane, decline of the ATP (adenosine triphosphate) level, exhaustion of the oxygen, etc.
In order to interfere the myocardial ischemia and protect myocardium, many drugs were developed in recent 20 years, e.g. β-receptor antagonist, calcium antagonist, transferase inhibitor, many kinds of free group scavenger, etc., whose protection effect on the myocardium cell in clinic is not affirmed yet. None of the existing medicine for treatment of ischemia myocardial can absolutely decreases the myocardial infarction and antagonizes the myocardial ischemia.
The available cardiovascular drugs, except for converting enzyme inhibitor that has the function of blocking the generation of growth factors, inhibiting protein synthesis and myocardial hypertrophy, do not have the function of regulating the growth, differentiation and rehabilitation of myocardium. In recent years, pharmacological treatment is emphasized overseas to induce the protection of myocardium cells themselves, such as promoting the myocardial regeneration by transduction gene etc, cardiotrophin and myotrophin. Moreover, extracellular signals are used to trigger various transmission mechanism to regulate the proliferation or reconstitution of myocardial and vascular cells. But all these researches are at the stage of animal test or preclinical study.
It is clearly demonstrated from the above studies that, in the situation that protection of myocardium by extracorporeal circulation is not consummated yet, it is necessary to provide a drug which can protect myocardium before, during or after surgery without any damage to the organism, interventions, which is important for exploring the prevention and cure of myocardial ischemia and reperfusion.
ZL94102798 discloses a growth-stimulation peptide of myocardial cells and the preparation method thereof. The process comprises the steps of: crushing the heart of healthy infant mammals other than a human with mechanical means, deeply freezing at −20° C. and heating to 60˜100° C. after being dissolved in water, then deeply freezing at −20° C. and centrifugating at 3000 rpm after being dissolved, and finally obtaining a polypeptide active substance with molecular weight less than 20000 Da through negative pressure interception column, sterilization, split charging, lyophilization and packing.
ZL94102799 discloses a growth-stimulating peptide of myocardial(GMGSP) that can stimulate DNA synthesis and protein synthesis of primarily cultured myocardial cells and that is isolated from the heart of healthy infant mammal. GMGSP is stable at PH 2˜9 and its biological activity does not change when being heated at 95˜100° C. for 10 minutes or at 60˜70° C. for 30 minutes; its biological activity is lost when being placed in proteolytic enzymes at 37° C. for 2 hours. A polymer is formed at 22° C.˜30° C. in aqueous solution without obviously changing in biological activity; biological activity does not change if GMGSP is lyophilized and sealed with 3%˜8% mannitol and stored at room temperature for 1.5 years, or at 4° C. for 2 years, or at −20° C. for 3 years. HPLC analysis indicates that the GMGSP is composed of 4 components each having biological activity, the relative peaks and retention times of which are 10.4% (2.88 min), 6.4% (3.93 min), 36.3% (5.09 min) and 7.3% (7.41 min), respectively. The molecular weight of two bands shown by SDS-PAGE analysis are respectively 8500 Da and 10800 Da, the average number molecular weight shown by HPLC analysis is 9800 Da and weight average molecular weight is 10500 Da, and both components have biological activity.
Chinese patent 03141352.8 with title of “cardio myopeptidin and the use thereof” discloses a cardio myopeptidin isolated from the heart of healthy infant mammal with the weight average molecular weight of less than 10000 Da, wherein the content of peptide is 75%˜90%; the content of free amino acid is 6%˜15%; the content of RNA is 1˜2%; the content of DNA is 3˜7%. It also discloses an use of the cardio myopeptidin for producing the medicament for treatment of cardiovascular disease and reperfusion injury. Chinese patent 03137133.7 discloses a preparation method of cardio myopeptidin, which comprises the steps of: cleaning and cutting the ventricle muscle of hearts of healthy non-human mammals, adding sterile distilled water and homogenizing, repeatedly freezing and thawing the homogenate for 3-4 times; heating to 65˜90° C. to remove the residue, filtering by the plate-and-frame filter to get a coarse filtrate, ultra-filtering the coarse filtrate with a hollow-fiber column to get a refined filtrate; ultra-filtering the refined filtrate by ultrafiltration membrane to intercept the cardio myopeptidin solution with the molecular weight less than 10000 Da; concentrating the solution by reverse osmosis, obtaining the product after filtration sterilization and lyophilization.
Above-mentioned study results indicate that the cardio myopeptidin, which contains several active contents, such as polypeptide, free amino acid, DNA etc, is isolated from the heart of healthy infant mammal other than a human mammal.
The polypeptides are linear chain protein compounds which are composed of various amino acids arranged in different sequence. These compounds always have strong physiological activity and functional specificity. Therefore, those polypeptides have a wide use for producing medicament for treatment of various diseases.
So far, there are no patents or documents disclosing the sequence and the use of polypeptides in cardio myopeptidin.